MME Incoming Call Control for ISR Handover
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Solution Overview
Problem
In the context of the 3GPP mobile network system, when a UE in the ECM-CONNECTED state moves from an MME-controlled location registration area to an SGSN-controlled area, incoming voice call notifications often fail due to the activation of the ISR feature, which prevents location registration and results in missed call notifications.
Innovation Solution
Implementing an incoming voice call control method that collaborates with the SGSN to send a response message indicating the UE's movement and re-attempts the call through the SGSN after a specified period, ensuring that incoming voice calls are successfully notified to the UE even during handover between registration areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the ISR feature is activated to reduce location registration processing, then network processing load and battery consumption are reduced, but incoming voice call notifications fail when UE moves between MME and SGSN areas
Solution Approach 1:
The MME proactively sends a service request message to the SGSN before the UE actually moves to the SGSN area, pre-establishing the communication path for incoming call notifications. This preliminary action ensures that when the UE moves and ISR would normally prevent location registration, the notification path is already established through the SGSN, preventing missed calls while maintaining the battery-saving benefits of ISR
Solution Approach 2:
The SGSN acts as an intermediary for incoming call notifications when the UE is in MME area but has moved to SGSN location registration area. The MME sends service request messages through the SGSN, which then forwards them to the UE. This intermediary mechanism allows reliable notification delivery without requiring the UE to perform location registration, thus maintaining both battery efficiency and call notification reliability
2Reliability
If location registration is performed frequently when UE switches between LTE and 3G areas, then incoming call notifications are reliable, but network processing load and battery consumption increase
Solution Approach 1:
Instead of waiting for the UE to perform location registration when moving between areas, the MME sends service request messages to the SGSN in advance. This preliminary action establishes the notification path before the UE actually needs it, eliminating the need for frequent location registration while maintaining reliable incoming call notifications, thus reducing both network load and battery consumption
3Loss of time
If the MME sends incoming call notification during UE handover, then call setup time is reduced, but the notification may not reach the UE if handover is in progress
Solution Approach 1:
The SGSN serves as an intermediary that receives service request messages from the MME and forwards them to the UE regardless of the UE's current area. This intermediary mechanism ensures that incoming call notifications are reliably delivered even during handover, as the SGSN can reach the UE through the appropriate access network without requiring the notification to wait for handover completion
Solution Approach 2:
The MME sends the service request message to the SGSN before the handover completes, proactively initiating the notification process. This preliminary action allows the notification to be in transit or already delivered by the time handover completes, reducing call setup time while the SGSN ensures reliable delivery through its intermediary position
Data Source
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AI summary
It is aimed to provide a mobility management device that can normally provide a UE with a notification of an incoming voice call made when ISR is activated and when a mobile communication device is moving from a location registration area under control of an MME to a location registration area under control of an SGSN. A mobility management device (10) makes an ISR feature operate in collaboration with an SGSN (20). It is assumed that a location registration area (60) managed by the mobility management device (10) exists within a location registration area (50) managed by the SGSN (20), and an incoming voice call is made to a mobile communication device (30) during when the mobile communication device (30) is moving out of the location registration area (60). The mobility management device (10) includes an incoming voice call control unit (11) that, in the above case, sends a response message indicating that the mobile communication device (30) is moving to a switching device (40) and, when an incoming voice call message is sent again from the switching device (40) to a switching device (40) after the lapse of a specified period of time, performs call attempt to the mobile communication device (30).